Pillow is a Python imaging library. Prior to version 12.3.0, the PcfFontFile._load_bitmaps() function read glyph dimensions from the PCF METRICS section and passed them directly to Image.frombytes() without calling Image._decompression_bomb_check(), allowing crafted PCF font data to cause excessive memory allocation, potentially exhausting system memory and causing a denial of service.

All Pillow releases older than 12.3.0 that perform PCF font loading, such as image processing pipelines, web applications, PDF renderers, or any code that accepts external font inputs, are affected. These applications rely on Pillow for font rendering and may process malicious font files to trigger the vulnerability.

The CVSS score of 7.5 classifies the issue as high severity. The EPSS score of less than 1% indicates a very low probability of exploitation, and the vulnerability is not included in the CISA KEV catalog. An attacker must supply a crafted PCF font file to an application that uses Pillow for rendering; because no readily available payloads or widespread exploitation are known, the overall risk is moderate despite the high severity metric.